1. Field of the Invention
The invention in general relates to water valves, and in particular to such valves that are operated by water pressure and are electrically actuated.
2. Description of the Prior Art.
Electrically operated water valves have been used for generations in appliances such as washing machines. Such valves generally have a magnetically responsive armature that alternately turns the water supply on and off as determined by the appliance programming. In order that the armature and the electrical power requirements be kept reasonably small, such valves generally are pressure operated: one side of the main valve seal is open to a operating pressure chamber; the armature is used to open and close a pilot valve which alternately places the operating pressure chamber at inlet pressure and at the outlet pressure; the resulting change in pressure in the operating pressure chamber causes the main valve to open and close. By making the inlet port of the operating pressure chamber very small compared to the outlet port, the operating pressure chamber inlet can be left open and the pressure in the operating pressure chamber can be regulated solely by opening and closing the outlet port; that is, when the outlet port is closed, the operating pressure rises to that of the inlet and when the outlet port is closed, the pressure drops to essentially that of the outlet, since the outflow is so much greater than the inflow. This allows the valve to be more compact and simple, but also allows water to flow continuously through the inlet and outlet ports of the operating pressure chamber while the valve is open. Examples of such pressure-operated water valves are disclosed in U.S. Pat. Nos. 4,387,878 and 4,534,537 issued to Zukausky, U.S. Pat. No. 3,593,957 issued to Dolter, U.S. Pat. No. 3,630,482 issued to Beller, U.S. Pat. No. 3,655,163 issued to Rattan, U.S. Pat. No. 3,672,627 issued to McCarty, U.S. Pat. No. 3,872,878 issued to Kozel, and U.S. Pat. No. 4,174,824 issued to Kolze. It is also known to use pressure operated pilot valves to regulate gas flow. See for example U.S. Pat. No. 3,917,219 issued to Fred W. Hendrick. The gas valve disclosed in the Hendrick patent also allows fluid to flow continuously through the an inlet port to the operating pressure chamber while the valve is open. This combination of tiny operating pressure chamber inlet ports and continuous flow through the port while the valve is open tends to cause the inlet ports to clog.